Micronutrients are a required component in crop nutrition in order to sustain life and produce an abundant harvest. Formally, micronutrients are nutrients required by organisms in small quantities to enable a range of physiological functions. Micronutrients are also referred to as “trace elements” because only small amounts are required to facilitate the desired functions. The micronutrients found in soil are quickly depleted in a growing season and must be supplemented by the addition of fertilizers. It is also known that not all fertilizers are compatible with all micronutrients. For example, certain micronutrients may disrupt the solubility of nutrients, reducing the overall bioavailability. This is especially apparent in the case of zinc supplements used in conjunction with phosphate fertilizers, which forms insoluble zinc phosphate and reduces the efficacy of the fertilizer.
There are currently many micronutrient fertilizers on the market today. These vary widely in their composition and concentration. While many commercial products are a combination of both macro- and micronutrients the current technology is a highly concentrated micronutrient fertilizer. Other products attempt to reach the same level of concentration as seen in the current technology but fail to do so while maintaining long term stability in a liquid form. A common method to increase stability and rheology for fertilizer suspensions is through the addition of clays, primarily bentonite. These clays are used up to a 10% loading to increase the rheology. The use of clays, commonly found in drilling fluids and agricultural products leads to soil deposits, drainage issues, and salt build-up. With the high loadings found in bentonite suspension, the overall nutrient concentration is lowered. In light of this, there is a need for aqueous micronutrient fertilizers that have excellent stability, can be readily diluted without much stirring, do not hard pack on settling, and contain a high concentration of insoluble and soluble micronutrients. Surprisingly, it was discovered that these dispersion characteristics can be achieved by combining insoluble and soluble micronutrients with a polyelectrolyte and a metal complexing agent.